Liquid crystal displays are commonly used as displays for compact electronic apparatuses. This is because they not only provide good quality images with little power consumption, but they are also very thin. The liquid crystal in a liquid crystal display does not emit any light itself. The liquid crystal has to be lit by a light source so as to clearly and sharply display text and images. Thus, a backlight module is generally needed for a liquid crystal display.
Referring to FIG. 8, a typical liquid crystal display 8 includes a liquid crystal panel 80, and a backlight module 90 positioned for providing light beams to the liquid crystal panel 80.
The backlight module 90 includes an optical film assembly 91, a light guide plate (LGP) 92, a plurality of light emitting diodes (LEDs) 93, and a plastic frame 94. The light guide plate 92, the optical film assembly 91, and the liquid crystal panel 80 are arranged in that order from bottom to top. The plastic frame 94 is used to accommodate the liquid crystal panel 80, the optical film assembly 91, the light guide plate 92, and the LEDs 93.
The light guide plate 92 is generally rectangular, and includes a light incident surface 921, a top light emitting surface 922 perpendicularly adjoining the light incident surface 921, a bottom surface 923, and two opposite side surfaces 924. The side surfaces 924 perpendicularly connect with the light incident surface 921, the light emitting surface 922, and the bottom surface 923. Each side surface 924 includes a pair of first ears 927 and a second ear 928 extending perpendicularly outward therefrom. The first ears 927 are located at opposite ends of the side surface 924, respectively. The second ear 928 is located in a middle of the side surface 924.
Each of the first ears 927 is half as thick as a main body of the light guide plate 92, and has a top surface coplanar with the light emitting surface 922. The second ear 928 is half as thick as the main body of the light guide plate 92, and has a base surface coplanar with the bottom surface 923. The light guide plate 92 can be made from polycarbonate (PC) or polymethyl methacrylate (PMMA), and can be manufactured by an injection molding method.
The plastic frame 94 includes two opposite first side walls 941 and two opposite second side walls 942. The first side walls 941 and the second side walls 942 are alternately arranged end to end. The first side walls 941 are longer than the second side walls 942. Each first side wall 941 defines a pair of first notches 947 and a second notch 948. The first notches 947 are located at opposite ends of the first side wall 941 respectively, and correspond to respective first ears 927 of the light guide plate 92. The second notch 942 is located in a middle of the first side wall 942, and corresponds to a respective second ear 928 of the light guide plate 92. One of the second side walls 942 defines a plurality of recesses 9420 to receive the LEDs 93.
Referring also to FIG. 9, the first ears 927 are inserted into the first notches 947, respectively. The second ears 928 are inserted into the second notches 948, respectively. Thus, the light guide plate 92 is received in and supported by the plastic frame 94.
In the process of assembly of the backlight module 90, the first ears 927 and the second ears 928 are generally pressed into the first notches 947 and the second notches 948 by applying manual force. This may result in the plastic frame 94 being distorted or even being damaged. When this occurs, the mechanical stability and the performance of the backlight module 90 are liable to be impaired.
What is needed, therefore, is a backlight module that can overcome the above-described deficiencies. What is also needed is a liquid crystal display including the backlight module.